Supplemental Financial Information (Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 15, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities		$ 70,070	$ 123,987	$ 87,221
Cash Flows from Investing Activities
Purchases of property, plant, and equipment		(11,399)	(10,779)	(12,373)
Acquisitions, net of cash acquired		(18,494)	(23,412)	(140,621)
Net proceeds from sale of property and equipment		13,096	953	26,500
Net proceeds from sale of business	$ 8,300	0	8,250	0
Net cash used in investing activities		(16,797)	(23,870)	(125,340)
Other, net		0	1,118	1,154
Cash Flows from Financing Activities
Long-term debt payments		(400)	(400)	(73,642)
Proceeds from long-term debt		0	0	73,242
Payment of debt issuance costs		0	(54)	(1,166)
Purchase of treasury stock at market prices		(2,872)	(1,539)	(956)
Intercompany financing		0	0	0
Net proceeds from issuance of common stock		674	3,341	1,801
Net cash (used in) provided by financing activities		(2,598)	1,348	(721)
Effect of exchange rate changes on cash		1,428	(146)	(2,912)
Net increase (decrease) in cash and cash equivalents		52,103	101,319	(41,752)
Cash and cash equivalents at beginning of year		170,177	68,858	110,610
Cash and cash equivalents at end of year		222,280	170,177	68,858
Gibraltar Industries, Inc.
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities		(15,172)	(34,243)	(13,309)
Cash Flows from Investing Activities
Purchases of property, plant, and equipment		0	0	0
Acquisitions, net of cash acquired		0	0	0
Net proceeds from sale of property and equipment		0	0	0
Net proceeds from sale of business			0
Net cash used in investing activities		0	0	0
Other, net			0	0
Cash Flows from Financing Activities
Long-term debt payments		0	0	0
Proceeds from long-term debt				0
Payment of debt issuance costs			0	0
Purchase of treasury stock at market prices		(2,872)	(1,539)	(956)
Intercompany financing		17,370	32,441	12,464
Net proceeds from issuance of common stock		674	3,341	1,801
Net cash (used in) provided by financing activities		15,172	34,243	13,309
Effect of exchange rate changes on cash		0	0	0
Net increase (decrease) in cash and cash equivalents		0	0	0
Cash and cash equivalents at beginning of year		0	0	0
Cash and cash equivalents at end of year		0	0	0
Guarantor Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities		83,114	140,890	94,977
Cash Flows from Investing Activities
Purchases of property, plant, and equipment		(11,026)	(10,321)	(11,754)
Acquisitions, net of cash acquired		(18,494)	(23,412)	(114,145)
Net proceeds from sale of property and equipment		12,905	230	26,500
Net proceeds from sale of business			0
Net cash used in investing activities		(16,615)	(32,385)	(98,245)
Other, net			1,118	1,154
Cash Flows from Financing Activities
Long-term debt payments		(400)	(400)	(73,642)
Proceeds from long-term debt				73,242
Payment of debt issuance costs			(54)	(1,166)
Purchase of treasury stock at market prices		0	0	0
Intercompany financing		(17,321)	(3,822)	(47,035)
Net proceeds from issuance of common stock		0	0	0
Net cash (used in) provided by financing activities		(17,721)	(4,276)	(48,601)
Effect of exchange rate changes on cash		0	0	0
Net increase (decrease) in cash and cash equivalents		48,778	104,229	(51,869)
Cash and cash equivalents at beginning of year		143,826	39,597	91,466
Cash and cash equivalents at end of year		192,604	143,826	39,597
Non-Guarantor Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities		2,128	17,340	5,553
Cash Flows from Investing Activities
Purchases of property, plant, and equipment		(373)	(458)	(619)
Acquisitions, net of cash acquired		0	0	(26,476)
Net proceeds from sale of property and equipment		191	723	0
Net proceeds from sale of business			8,250
Net cash used in investing activities		(182)	8,515	(27,095)
Other, net			0
Cash Flows from Financing Activities
Long-term debt payments		0	0	0
Payment of debt issuance costs			0	0
Purchase of treasury stock at market prices		0	0	0
Intercompany financing		(49)	(28,619)	34,571
Net proceeds from issuance of common stock		0	0	0
Net cash (used in) provided by financing activities		(49)	(28,619)	34,571
Effect of exchange rate changes on cash		1,428	(146)	(2,912)
Net increase (decrease) in cash and cash equivalents		3,325	(2,910)	10,117
Cash and cash equivalents at beginning of year		26,351	29,261	19,144
Cash and cash equivalents at end of year		29,676	26,351	29,261
Eliminations
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities		0	0	0
Cash Flows from Investing Activities
Purchases of property, plant, and equipment		0	0	0
Acquisitions, net of cash acquired		0	0	0
Net proceeds from sale of property and equipment		0	0	0
Net proceeds from sale of business			0
Net cash used in investing activities		0	0	0
Other, net			0
Cash Flows from Financing Activities
Long-term debt payments		0	0	0
Payment of debt issuance costs			0	0
Purchase of treasury stock at market prices		0	0	0
Intercompany financing		0	0	0
Net proceeds from issuance of common stock		0	0	0
Net cash (used in) provided by financing activities		0	0	0
Effect of exchange rate changes on cash		0	0	0
Net increase (decrease) in cash and cash equivalents		0	0	0
Cash and cash equivalents at beginning of year		0	0	0
Cash and cash equivalents at end of year		$ 0	$ 0	$ 0